1. Field of the Invention
The present invention relates to an image forming apparatus in which an image is formed on a recording medium using a thermal transfer sheet and a protective layer that protects a surface of the image is formed. More particularly, the present invention relates to an image forming apparatus that modifies a surface state of the protective layer (formed on the image of the recording medium) to give it, for example, glossiness or a mat tone, and that takes measures against dust to improve the quality of a surface state of a printed material; and relates to a modification sheet cartridge using the image forming apparatus.
2. Description of the Related Art
As a related image forming apparatus, a sublimation apparatus that forms an image by transferring a dye layer of a thermal transfer sheet onto a recording medium is available. In this type of apparatus, a transparent protective layer for protecting a surface of the image formed on the recording medium is formed on the image. The protective layer has, for example, the function of shielding the image from gas that causes the image to deteriorate, the function of preventing discoloration and fading of the image caused by absorption of ultraviolet light, the function of preventing, for example, dye (forming the image) from flowing onto various plastic articles, such rubber, the function of preventing wearing of the image, and the function of protecting the image from sebum.
The above-described protective layer is provided by, for example, laminating it upon a ribbon base sheet, and is thermally transferred onto the image by a thermal head. By being thermally transferred onto the image, the protective layer can prevent, for example, curling of the recording medium, as well as protect the image. When the protective layer is thermally transferred using the thermal head, it is possible to arbitrarily change thermal energy from the thermal head to form a very small uneven pattern, so that its surface is subjected to surface treatment to give it, for example, glossiness or a mat tone.
In addition, in the related image forming apparatus, a recording medium having a receiving layer (which receives dye) formed on a thermoplastic base material is conveyed, and a thermal transfer sheet having a dye layer and a protective layer formed side by side on a sheet in a travel direction is caused to travel. While the receiving layer of the recording medium and the dye layer of the thermal transfer sheet oppose each other, thermal energy is applied by the thermal head, to thermally transfer the dye layer of the thermal transfer sheet to the receiving layer of the recording medium, so that an image is formed. While the image formed on the recording medium and the protective layer of the thermal transfer sheet oppose each other, thermal energy is applied by the thermal head, to thermally transfer the protective layer of the thermal transfer sheet onto the image formed on the recording medium (refer to, for example, Japanese Unexamined Patent Application Publication No. 2007-76332).